"I will be receiving a Form 5498 in April 2025 for a rollover of a Dec 2024 payment for my 2024 RMD."
RMDs cannot be "reduced." They are required distributions, meaning that the RMDs are not eligible for rollover. If you deposited any of the 2024 RMD into an IRA, it is an ordinary contribution, not a rollover, regardless of how it might be shown on the Form 5498. When you tell TurboTax the amount of the distribution that was RMD, TurboTax will prevent you from indicating the RMD as having been rolled over.
If your distribution in December 2024 was more than your 2024 RMD, the amount distributed beyond the amount of your 2024 RMD was eligible for rollover and TurboTax will allow you to report that portion as having been rolled over. In that case you'll need to indicate that you moved the funds to another retirement account and that you rolled over only part of the distribution.
